The ability to quickly determine the root cause of processing faults, such as particle contamination, film non-uniformity, wafer placement errors or other faults, in the production of a semiconductor wafer is confounded by the number of possible defect sources and the random wafer paths within the tool. For example, it is not uncommon to find aluminum particles on periodic particle qualification monitor wafers after processing in a semiconductor processing tool. However, because a large percentage of the tool may consist of aluminum, it is very time consuming to find the source of the aluminum particles using present troubleshooting methods.
One present-day method for detecting faults in the processing of wafers by a semiconductor production tool in a device fabrication facility is the periodic testing of the tool using test wafers. This testing method typically is performed at predetermined cycles, for example, every four to eight hours. However, between testings the fault may become catastrophic, that is, an unacceptable number of production wafers may become contaminated or otherwise damaged. Thus, the production yield could be significantly reduced before the fault is detected.
Other methods for fault detection in a tool include “wafer-based unit operation regression testing”, which requires a wafer to be tested after every step of a process flow, and “causal magnification”, which requires components of the tool to be operated in isolation a number of times, for example, the opening and closing of a valve a number of times, to identify the component of the tool causing the faulty condition. However, these and other methods consume a lot of time, wafers and other resources, and in many cases are not successful. If unsuccessful, then wholesale replacement of multiple components may be required to identify and resolve the problem. The longer the production tool is out of operation, the more costly the problem becomes.
Accordingly, it is desirable to provide methods for detecting a processing fault of a semiconductor fabrication or processing tool during early stages of the fault onset. In addition, it is desirable to provide fault detection apparatuses for semiconductor fabrication or processing tools that are capable of detecting processing faults efficiently. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.